Boldfaced statements are parts of the original essay (or a subsequent reply) to which the respondent has directed his comments.Italicized/emphasized comments prefaced by (R) are those of the respondent and are presented unedited.
My replies appear under the respondent's comments in blue text and are prefaced by my initials (MB).

(R) The "year" of 1582 had only 355 days, and everybody adjusted. Why not just declare that the Twentieth century will only have 99 years. That should fix it!(MB) The calendar adjustment in 1582 was done in order to bring the Julian calendar back in alignment with the seasons. The fix (called the "Gregorian" calendar) produced few problems since that day and age was nowhere near as dependant on the calendar as we are today.
As to your solution, it would be better to retroactively declare that the *first* century had only 99 years. Besides the fact that nothing would actually be affected, when those years were "the present", the BC/AD (or BCE/CE, as I have come to prefer) system of numbering years hadn't even been invented yet. Those people who lived during that time certainly didn't know that they were living in the first century.
Of course, the ultimate solution to the question of when a millennium/century/decade ends is to define when it *starts*. Since the first one began in the year 1 CE, the ending would have to be in 2000 CE.